Powerful magnitude-4.1 aftershock rattles Southern California

Martin Jimenez cleans up broken glass from the front window of a former tile store Saturday after a magnitude-5.1 earthquake centered near La Habra shook the area Friday night.
Keith Durflinger – Staff Photographer

Residents are displaced Saturday at an apartment building on the 2700 block of Associated Road in Fullerton after Friday’s magnitude-5.1 earthquake near La Habra.
Keith Durflinger — Staff Photographer

A magnitude-4.1 aftershock hit parts of Southern California on Saturday afternoon, the largest of more than a hundred such aftershocks of Friday night’s magnitude-5.1 earthquake that shook homes and businesses throughout Los Angeles and Orange counties.

The 4.1 temblor struck just after 2:30 p.m., according to the U.S. Geological Survey, which also recorded two foreshocks Friday, measuring magnitudes of 3.6 and 2.1.

The magnitude-5.1 earthquake centered just east of La Habra on Friday night was felt throughout the region, however the damage it caused was primarily isolated to a pocket of northern Orange County, where 26 homes were red-tagged, officials said.

Dozens of aftershocks continued to rumble through the night, including one measured at magnitude 3.6 at 9:30 p.m. Friday, and another measured at magnitude 3.4 at 9:02 a.m. Saturday, according to the USGS.

And more are expected, USGS Geophysicist Doug Given said.

“This is fairly typical aftershock activity for an event this size. This is maybe a little on the energetic side,” he said.

“We have been saying there is about a 5 percent chance of a larger earthquake to come,” he said. But as time passes, large aftershocks become increasingly less likely to occur. “That likelihood is decaying very rapidly.”

“We have a long ways to go,” USGS seismologist Lucy Jones said. “It will be months and months before we’re down to a rate of one a month in that area, which is where it was before the main shock.”

She pointed out that until Friday, there had only been two quakes measuring above a magnitude-5.0 in the Los Angeles area since the 1994 Northridge earthquake. In the decade prior to that devastating quake, there were several large-magnitude earthquakes.

“This has been the quietest decade in some time.”

Friday’s quake rattled windows and nerves throughout Orange and Los Angeles counties, but Fullerton was hardest hit by the quake.

As officials made damage assessments overnight and into Saturday, 20 apartment units and six houses in Fullerton were deemed uninhabitable and red-tagged, Fullerton police Sgt. Mike Chlebowski said.

Residents would not be allowed to reoccupy the homes until they were checked out by an inspector, he said.

And work on a ruptured water main at Rosecrans Avenue and Gilbert Road Street continued to force a road closure Saturday morning, Chlebowski said. Fullerton city officials reported 13 water main breaks in all.

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But no earthquake-related injuries had been reported Saturday, in Fullerton or elsewhere.

No buildings had been red-tagged, though a couple dozen La Habra residents had evacuated their homes voluntarily due to safety concerns, Davis said.

Authorities had initially feared possible structural damage at three apartment buildings that were especially rocked by the quake in the 2500 block of West Whittier Boulevard, the 400 block of North Idaho Street and the 700 block of West First Avenue, Davis said.

Considering how close La Habra lies to the earthquake’s epicenter, “We fared pretty well,” he said.

“The La Habra Police Department has received multiple reports of broken windows throughout the community, with some areas reporting natural gas smells,” La Habra city officials said in a written statement.

“Gas was shut off in the 1200 block of (South) Beach (Boulevard), as a precautionary measure. LA Fitness, which is located in one of the shopping complexes near the intersection of Imperial (Highway) and Beach (Boulevard), had water running off the roof. At Beach (Boulevard) and Lambert (Road), the traffic signal was hanging precariously, but it has since been removed.”

About 200 Southern California Gas Company customers were without service as crews rushed to fix leaks and restore service to customers whose gas was shut off by earthquake valves, according to the utility. Those who suspect a natural has leak were advised to leave the area immediately and report the leak by calling 800-427-2200.

A ruptured pipe caused water to flow from the ceiling of a Rite Aid Pharmacy along Colima Road, but the issue was handled within about 20 minutes, Los Angeles County Fire Department Dispatch Supervisor Cheryl Sims said. Officials had previously reported the incident as occurring at a pharmacy along Nogales Street.

Near Brea, a rockslide along Carbon Canyon Road was blamed for causing a car to overturn, Brea police said. The crash resulted in only minor injuries, however the roadway near the county line remained closed Saturday.

The Red Cross set up an evacuation shelter at the La Habra Community Center, 101 W. La Habra Boulevard, where 38 people spent the night, Red Cross spokeswoman Meredith Mills said. It remained open through Saturday morning.

“We’re definitely here to help people if they need it,” Mills said.

A preliminary survey found “no significant reports of damage” in Los Angeles County, according to a statement issued by the Los Angeles County Office of Emergency Management.

Los Angeles County’s bridges and other infrastructure were also free from reported damage Saturday, Los Angeles County Department of Public Works officials said.

Friday’s earthquake was believed to be associated with the far east end of the Puente Hills Thrust fault system, Given said. “This is the fault system that, on its northern edge, was responsible for the Whittier Narrows Earthquake in 1987,” Given said. Prior to the Whittier Narrows earthquake, the fault system had been unknown.

Scientists in Pasadena had a four-second warning before the shaking reached them from the La Habra area thanks to an experimental early warning system that’s been in operation for two years, Given said.

Given said he hoped increased funding on the federal and national levels would soon help bring the technology to the mainstream, as has been done in Japan and Mexico City.

Tom Connolly, a Boeing employee who lives in La Mirada, the next town over from La Habra, said the magnitude-5.1 quake lasted about 30 seconds.

“We felt a really good jolt. It was a long rumble and it just didn’t feel like it would end,” he told The Associated Press by phone. “Right in the beginning it shook really hard, so it was a little unnerving. People got quiet and started bracing themselves by holding on to each other. It was a little scary.”

Friday’s quake hit a week after a pre-dawn magnitude-4.4 quake centered in the San Fernando Valley rattled a swath of Southern California. That jolt shook buildings and rattled nerves, but did not cause significant damage.

Given said that quake was not associated with the same fault system believed responsible for Friday’s earthquake near La Habra.

Officials throughout the region said the earthquake was a stark reminder for California residents to be prepared for earthquakes with supplies and plans.

“Clearly we cannot predict earthquakes, we can only say things about the statistics of earthquakes,” Given said. “Based on the best science of the faults and the earthquake history in Southern California, in the Los Angeles region, there’s a 97 percent chance in the next 30 years of a magnitude 6.7 or larger.”

Staff Writer Kelly Goff and The Associated Press contributed to this report.